Machining operations involve the removal of metal from the surface of a rotating work piece by a cutting tool which generates a chip during the machining process. The chip preferably breaks to prevent long chip strings from engaging the rotating workpiece. Long chip strings are also more difficult to handle and consume more space than the equivalent length of short chips. A good deal of attention accordingly is paid by those skilled in the art to the formation of the chip during the machining process. Also, a significant amount of energy may be consumed in the movement of the chip away from the cutting tool, and in the technique for repeatedly breaking the chip to prevent long chips from being formed.
A discontinuous chip has a relatively short length before it breaks off from another chip during the machining process, and is desirable since the discontinuous chip may be easily cleared away from the cutting tool. While some metals and alloys easily generate discontinuous chips during metal cutting operation, other metals and alloys produce chips which do not readily break off, and in those cases machinists prefer a cutting tool with enhanced chip control features. Without an effective chip control mechanism, chips resulting from some metal working operations may form a curl, but the chip length undesirably continues in this curled manner without the chip breaking. These long chips often may not be easily removed from the area of the rotating workpiece. Safety regulations are increasingly requiring that long chips not be formed by machining operations to prevent injury to operators from shavings being whipped around when they get caught on the rotating chuck or workpiece. Long or continuous cutting chips are also more difficult to handle and transport to a metal reclamation site than short discontinuous chips. Cutting inserts with chip control features are disclosed in U.S. Pat. Nos. 4,116,576 and 4,963,060.
Cutting inserts are commonly used in machining operations wherein the cutting insert is intended to be discarded when the cutting edges become dull and chipped. A common type of cutting insert is detachably clamped to a tool holder and is indexable or invertible. The insert thus has at least two primary cutting edges, such that once one cutting edge is worn the tool may be inverted and the other cutting edge used before the insert is discarded.
One of the problems with a conventional cutting insert having a chip control pocket is that the chip tends to scrap a side wall of a chip control pocket as it travels into and/or out of the pocket. This allows the chip to get "hung-up" in the pocket so that a subsequently formed chip is prevented from cleanly entering and/or exiting the pocket. Another problem with cutting inserts with conventional chip control features is that the chip control pocket generates a large amount of heat, which decreases the useful life of the insert. Accordingly, a cutting insert with an improved chip control mechanism is desired by those skilled in metal machining operations, particularly if the cutting insert can be manufactured at an economical price compared to conventional cutting inserts. Those skilled in the art have thus long desired a cutting insert with chip control features which will reliably result in discontinuous chips, and wherein the discontinuous chips smoothly pass into and out of the chip control pocket without generating excessive heat.
The disadvantages of the prior art are overcome by the present invention. An improved cutting insert is hereinafter disclosed which desirably results in discontinuous chips. The cutting insert of the present invention is well suited for use in machining operations which otherwise would tend to produce continuous chips, or which would not reliably produce discontinuous chips, or which would produce discontinuous chips but would also result in poor life of the cutting insert.